Acetic acid-sodium acetate buffer

Reagents. In view of the sensitivity of the method, the reagents employed for preparing the ground solutions must be very pure, and the water used should be re-distilled in an all-glass, or better, an all-silica apparatus the traces of organic material sometimes encountered in demineralised water (Section 3.17) make such water unsuitable for this technique unless it is distilled. The common supporting electrolytes include potassium chloride, sodium acetate-acetic acid buffer solutions, ammonia-ammonium chloride buffer solutions, hydrochloric acid and potassium nitrate. 

Both HMR and MR have strong absorption peaks in the visible portion of the spectrum the colour change interval from pH 4 to pH 6 can be conveniently obtained with a sodium acetate-acetic acid buffer system. 

Sodium acetate-acetic acid buffer. Prepare a solution which is 0.2 M in sodium acetate and 0.8 M in acetic acid. The pH is 4.0. 

Pal, B., Sen, P.K. and Sen Gupta, K.K. (2001) Reactivity of alkanols and aryl alcohols towards tetrachloroaurate(lll) in sodium acetate-acetic acid buffer medium. Journal of Physical Organic Chemistry, 14, 284. 

Figure 7. V versus to 1/2 plots for Al3+ in sodium acetate-acetic acid buffer...

J(P1)720>. These cyclizations were mediated with sodium acetate-acetic acid buffers affording moderate to good yields (52-86%) and low to moderate yields (10-60%) of 7-acyl-substituted 1H- and (mesoionic) 2//-pyrrolote-trazole derivatives 67a-g, and 70a-d and 70f-h, respectively. In most cases, deacylation of pyrrolotetrazoles 67 and 70 could be effected easily by heating with HC1 affording moderate to excellent yields of 68a-e and 71a-e. 

The preparations proved to be 98 to 99% chromatographically pure, the contaminant always being the other isomer. The various absorption maxima are reported in Table I. All solutions were 0.01 M in complex. Those designated as HC or HT were measured either in water at pH 5-6, or in O.lM sodium acetate-acetic acid buffer at pH 5.5 (no spectral differences resulted) and those designated C or T were adjusted to pH 10.5 with ethylenediamine. 

Solochrome Violet R [2092-55-9] M 367.3. Converted to the monosodium salt by pptn with sodium acetate/acetic acid buffer of pH 4, then purified as described for Chlorazole Sky Blue FF. Dried at 110°. It is hygroscopic. [Coates and Rigg TFS 57 1088 1961],... 

The desired relationship between pretazettine (242) and haeman-thidine (248) was achieved when 248 was oxidized to 250, converted, in turn, with sodium acetate-acetic acid buffer at reflux to 244, thus establishing a structural and stereochemical link between 242 and 248. At C-ll haemanthidine bears a hydroxy group directed toward the C-l-C-2 unsaturation, and since it seemed mechanistically... 

Parkash and Bansal reported the detection and determination of microgram quantities of ethylenediaminetetraacetic acid with molybdophosphoric acid by a spectrophotometric method [25]. For the detection of EDTA, 5 to 10 Amberlite IRA-400 resin beads (hydroxide form) were placed on a white spot-plate and blotted dry. One drop of sample solution was added, followed by one drop of 4% molybdophosphoric acid solution. A blue color develops if EDTA is present. For the determination, the sample solution (2 mL, containing 18.6 to 186 pg of EDTA) and 4% molybdophosphoric acid solution (3 mL) are mixed for 5 minutes and diluted to 10 mL with water or sodium acetate-acetic acid buffer solution of pH 2. The absorbance is measured at room temperature at 690 nm against a reagent blank. 

Dansyl amino acids Aqueous sodium acetate/ acetic acid buffer/ acetonitrile 360 490... 

MET-CAMO was prepared from 5/ -methylthebaine (57) [109,110] via 14/ -amino-7,8-dihydro-5/ -methylcodeinone (59) which was obtained by the Kirby-McLean procedure [111]. Thus, oxidation of 2,2,2-trichloroethyl A-hydroxycarbamate with sodium periodate in the presence of 5/ -methylthebaine gave the adduct (58). Catalytic hydrogenation using a Pd/C catalyst in methanol in the presence of sodium acetate-acetic acid buffer yielded amine (59). Reaction with 4-nitrocinnamoyl chloride furnished amide (60) and ether cleavage using boron tribromide yielded MET-... 

In 1947, Hudson et al. (H15) developed a method for acid phosphatase which, like the procedure of Bessey et al. for alkaline phosphatase (B16), was based upon the use of p-nitrophenyl phosphate as substrate. The buffer substrate solution consisted of equal volumes of a 0.1 M sodium acetate-acetic acid buffer, pH 5.4, and 0.001 M magnesium chloride and of a 0.4% solution of approximately 50% pure disodium p-nitrophenyl phosphate in 0.001 N HCl. To 1 ml of this solution, 0.1 ml of the serum sample was added. The final concentrations in this reaction mixture were 0.045 M acetate buffer, pH 5.4 magnesium chloride. 0.00045 ilf substrate, 0.004 M. The reaction was allowed to run for 30 minutes at 38°C, and the reaction was stopped by the addition of sodium hydroxide. The liberated yellow p-nitrophenol was read at 400 nm and the amount was... 

Methods involving LLE were developed for determination of phenol and other phenolic compounds. For example, for simultaneous determination of phenol, hydroquinone (66) and catechol (42) in urine, the samples were subjected to acid hydrolysis, saturation with sodium sulfate and LLE with diethyl ether. End analysis was by RP-HPLC on a Ci8 column, elution with sodium acetate-acetic acid buffer-acetonitrile gradients, and ELD. The recovery and reproducibility were generally over 90%. The method appears to be more sensitive than GC or HPLC with UVD. It is proposed for cigarette smokers and refinery workers exposed to low benzene concentrations. Good recoveries of these metabolites was attained at 0.1 to 50 mgL concentrations, with coefficients of variation of a few percent, both for within a day and between day determinations. ... 

Thus, a sodium acetate-acetic acid buffer s capacity is maximum when equimolecular concentrations are taken in their mixture the pH becomes 4.74 (for Ka = 1.82 x 10 ). When the ratio salt/acid is varied, the buffer will have a different pH, but not far away from the value of pKa. The maximum variation in the acid salt ratio allowed is 1 10 or 10 1. The limiting values of the buffer pH becomes... 

Table II. The Determination of Eo for the pH Scale at 25°, with Sodium Acetate-Acetic Acid Buffers...

Figure 2. Typical gas volume data for the absorption of gaseous Oe into a bisulfite solution. Sodium acetate-acetic acid buffer at 0.5 M initial [HSOf] = 0.012 M [0 ] = 1.23 X 10 3 M. Insert O, 0 absorption into H20 , initial 02 absorption into HSOi solution.

In general, a buffer system can be represented as salt-acid or conjugate base-acid. Thus the sodium acetate-acetic acid buffer system discussed above can be written as CHgCOONa/CHgCOOH or simply CHgCOO-ZCHgCOOH. Figure 16.1 shows this buffer system in action. 

The pH of a sodium acetate-acetic acid buffer is 4.50. Calculate the ratio [CH3COO ]/[CH3COOH]. 

Mobile phase MeCN MeOH 25 mM pH 4.8 sodium acetate-acetic acid buffer 35 45 20... 

The natural smectite hectorite, when obtained from the Clay Repository of the Clay Minerals Society, still contains a lot of carbonate impurities. In order to eliminate these impurities, hectorite has to be pretreated with a sodium acetate/acetic acid buffer of pH 4 [53]. In this way, all carbonates are transformed into H2CO3, whereupon H2O and CO2 (liberated from the solution) are formed. Subsequent exchange in a NaCl solution and removal of the excess chloride give Na+-hectorite. The synthetic laponite, supplied by Laporte Inorganics, is already in the Na -form and free of any impurity. 

Procedure. A drop of the HCl solution of the sample is treated in a micro test tube with one drop each of sodium acetate-acetic acid buffer (pH 5.5),... 

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